Predatory mite Amblyseius orientalis prefers egg stage and low density of prey Carpoglyphus lactis

Amblyseius orientalis (Ehara) (Acari: Phytoseiidae) is an effective predatory mite for spider mites control on fruit trees in China. In recent decade, it can be produced commercially and intensively via Carpoglyphus lactis (Linnaeus) in natural enemy factory. During the practical predator production, ratio of predatory mites to their prey was found critical for the population increase of A. orientalis in large-scale rearing. In this study, we investigated the predatory capacity of A. orientalis on different developmental stages of the prey C. lactis and the effect of prey numbers on predator reproductions. The maximum predation number of A. orientalis adults on C. lactis adults was 2.21 at the lowest density of 5 and on C. lactis eggs was 45.07 at the highest density of 60. The preference index Ci of A. orientalis on C. lactis eggs and adults was 0.4312 and − 0.9249, respectively, suggesting that A. orientalis preferred eggs to adults of C. lactis. A. orientalis could reproduce when it preyed either eggs or deutonymphs of C. lactis. However, the fecundity of the predatory mites is not proportional to the provided prey density in a week. Higher density of prey deutonymphs resulted in lower fecundity, while more prey eggs can bring higher fecundity of A. orientalis. Therefore, our study indicated that suitable density and developmental stage of prey is the basis for A. orientalis production in a large scale.